Fontlab Studio 5.1.2 aalt feature

I just upgraded my FontLab studio. When I compile features I get this type of warning now about the aalt feature:
[WARNING] feature 'liga', referenced in aalt feature, either is not defined or had no rules which could be included in the aalt feature.
It still compiles, but has something changed about this feature?

Nothing has changed about this feature. The new FDK version build in FontLab now tells you that it makes no sense to include features with ligature lookups in order to build a feature with a 'select one from many' lookup. The old FDK has ignored it silently.